Dynamic MR images possess various transformation symmetries,including the rotation symmetry of local features within the image and along the temporal dimension. Utilizing these symmetries as prior knowledge can facilitate dynamic MR imaging with high spatiotemporal resolution. Equivariant CNN is an effective tool to leverage the symmetry priors. However, current equivariant CNN methods fail to fully exploit these symmetry priors in dynamic MR imaging. In this work, we propose a novel framework of Spatiotemporal Rotation-Equivariant CNN (SRE-CNN), spanning from the underlying high-precision filter design to the construction of the temporal-equivariant convolutional module and imaging model, to fully harness the rotation symmetries inherent in dynamic MR images. The temporal-equivariant convolutional module enables exploitation the rotation symmetries in both spatial and temporal dimensions, while the high-precision convolutional filter, based on parametrization strategy, enhances the utilization of rotation symmetry of local features to improve the reconstruction of detailed anatomical structures. Experiments conducted on highly undersampled dynamic cardiac cine data (up to 20X) have demonstrated the superior performance of our proposed approach, both quantitatively and qualitatively.

本研究旨在解决现有等变卷积神经网络在动态磁共振成像中未能充分利用旋转对称性的问题。提出了一种新颖的时空旋转等变卷积神经网络框架（SRE-CNN），通过设计高精度滤波器和构建时序等变卷积模块，充分利用动态MR图像的旋转对称性。实验结果表明，该方法在高达20倍欠采样的动态心脏影像重建中表现优越。 

具时空旋转等变性的卷积神经网络（SRE-CNN）用于心脏动态磁共振成像